Method of making fiber reinforced metal matrix products

ABSTRACT

A METHOD OF CASTING A METAL FIBER RIBBON ONTO A METAL MATRIX FOIL TO FORM A FIBER REINFORCED METAL MATRIX SPECIMEN. THE METHOD IS CHARACTERIZED BY IMPINGING A MOLTEN METAL ONTO THE MOVING SURFACE OF METAL MATRIX FOIL IN SUCH A MANNER THAT THE METAL RIBBON FIBER ADHERES TO THE MATRIX FOIL.

May 1973 In A K ETAL 3,734,762

METHOD OF MAKING METAL FIBER REINFORCED METAL MATRIX PRODUCTS Filed June 25, 1971 INVENTORS LLOYD E HA MAN CARROLL EM EY Cemnamo JC-omAf-aa 8" 3041a! ATTORNEYS United States Patent 3,734,762 METHOD OF MAKING FIBER REINFORCED IVETAL MATRDt PRODUCTS Lloyd E. Hackman, Worthington, and Carroll E. Mobley,

Upper Arlington, Ohio, assignors to Ribbon Technology Corporation, Columbus, Ohio Filed June 25, 1971, Ser. No. 156,694 Int. Cl. C23c 7/00 US. Cl. 117-37 R 4 Claims ABSTRACT OF THE DISCLOSURE A method of casting a metal fiber ribbon onto a metal matrix foil to form a fiber reinforced metal matrix specimen. The method is characterized by impinging a molten metal onto the moving surface of metal matrix foil in such a manner that the metal ribbon fiber adheres to the matrix foil.

BACKGROUND Tapes and wide goods are one of the principal building blocks used in the fabrication of composite structures. While metal fiber reinforced organic matrix tapes and wide goods are readily available, metal fiber reinforced metal matrix products are not generally available at reasonable cost for many composite systems.

Prior to the present disclosure, fiber reinforced metal matrix products Were produced by complex methods and required expensive apparatus wherein a drawn or rolled solid metal fiber was pressure-bonded to a metal matrix foil. The product so formed was of limited availability because in most composite structure applications the cost was prohibitive.

Melt spinning techniques are widely known in which one or more molten metal streams are impinged onto a moving chill surface. In these processes, however, the cast metal filament is solidified on the chill surface and thrown off to form a continuous metal filament which in most cases, is not in a form which could conveniently be used to form fiber reinforced metal matrix products. Even if the fibers so formed could be used, they heretofore would still have to be pressure bonded by the highly expensive prior art process which would not solve the problem of prohibitive cost for wide spread use in composite structures.

The prior art also teaches casting a continuous layer of molten aluminum in a thin film form onto a steel base which has been coated with cobalt nickel as evidenced by US. Pat. 2,611,163. However, this type of bimetallic structure is not as desirable as a plurality of discrete finite sized films bonded to the matrix foil. One of the major purposes of the fiber reinforcing construction is to resist the propagation of fracture cracks which a continuous sheet of film does not accomplish.

GENERAL DESCRIPTION The method of the present disclosure comprises, in general, impinging a stream of molten metal onto the surface of a rapidly moving metal matrix foil to effect the solidification of the molten stream to a metal ribbon fiber adhered to the surface of the foil in such a manner as to provide reinforcement to the foil. In one embodiment of the present invention, the molten stream is impinged onto the inner surface of a rapidly rotating cylindrical drum. The inner surface of the drum is lined with the metal matrix foil which may be removed from the drum after the ribbon fiber has been deposited there- In another embodiment, a plurality of molten metal streams are impinged upon the surface of rapidly moving continuous band or belt. The belt comprises the metal matrix foil and the molten metal is solidified thereon in ribbon fiber form.

The fiber reinforced metal matrix foils may subsequently be used in the fabrication of laminated composites using conventional processing techniques.

OBJECTS It is therefore a primary object of the present disclosure to provide a method of producing a metal fiber reinforced metal foil in a relatively efficient and economical manner which may be subsequently used in the fabrication of fiber reinforced metal composite structures.

It is another object of the present disclosure to provide a method of the type described wherein the metal reinforcing fiber may be cast directly onto the surface of the foil in tightly adhering relationship thereto.

It is another object of the present disclosure to provide a method of the type described wherein the metal reinforcing fiber may be cast in molten form onto the metal foil in a predetermined configuration relative to width and depth to provide greater reinforcing properties and versatility at relatively low cost.

It is still a further object of the present disclosure to provide a method of the type described wherein a single stream of molten metal can be cast onto the surface of the matrix foil disposed on the inner surface of a rotating cylindrical drum at a predetermined helical angle to orient the fiber pattern upon the foil to produce a fiber reinforced metal matrix wide goods product in a most desirable yet relatively simple manner.

IN THE DRAWINGS FIG. 1 is a diagrammatical perspective view of one type of apparatus used in the practice of the method of the present invention; and

FIG. 2 is a diagrammatical view of another apparatus used to practice the method of the present invention.

DETAILED DESCRIPTION OF INVENTION In accordance with the disclosed method, FIG. 1 illustrates an apparatus which includes a molten metal reservoir 20 which is provided with a plurality of nozzles through which a plurality of molten metal streams 22 are impinged upon the surface of a continuous, rapidly moving belt 24. Belt 24 preferably comprises a metal matrix foil fed from a rotating spool 26 and gathered by a take-up spool 28. The spools may be driven and operated in any well-known conventional manner.

A means for rapidly cooling the molten streams 22 is provided in the form of a fluid-cooled heat sink 30 which is in heat conducting relationship with that portion of belt 24 upon which streams 22 impinge.

'It is well-known that a molten stream of metal upon striking a rapidly moving cool surface tends to form. a generally thin rectangular configuration. By appropriately controlling the process parameters, such as stream velocity, diameter, and temperature and belt speed, surface finish and temperature, the size and shape can be controlled to obtain a predetermined width and thickness of the metal ribbon formed.

However, the prior art has taught only the formation of cast metal filaments which are thrown off the chill surface for collection.

It has been discovered, however, that certain process parameters may be selected wherein the molten stream upon solidification adheres tightly to the metal chill surface in the form of a metal matrix foil to form a metal ribbon fiber reinforced metal matrix specimen.

The parameters which effect the successful production of these fiber ribbon reinforced metal matrix specimens include the following:

(1) the casting properties of the molten metal such as the superheat, latent heat of fusion and the surface tension.

(2) The thermal properties of the foil such as the foil temperature and thermal conductivity.

(3) The surface finish of the foil such as the roughness and cleanliness.

(4) The manner in which the molten metal stream is carried by the moving foil surface to reduce any forces which tend to separate the ribbon fiber from the foil before complete solidification and bonding takes place.

(5) To a more limited degree, the choice of the molten metal relative to the metal comprising the matrix foil.

Using the apparatus described in FIG. 1, the production of fiber ribbon reinforced metal matrix tapes would be extremely convenient. Belt 24 would consist of the metal matrix foil in the desired thickness and width. The end product consisting of the solidified metal ribbon fibers adhered to the foil would be taken upon on spool 28.

Another apparatus is diagrammatically illustrated in FIG. 2 and is generally more convenient for the production of what is termed wide goods in the field of fiber reinforced matrix specimens for the fabrication of composite structures.

A large rotating cylindrical metal drum 40 is provided with the metal matrix foil 42 detachably mounted in surrounding relationship to the inner surface of the drum. The drum functions as both a carrier and a heat sink for the foil which rapidly chills the molten metal stream. It should be understood that drum 40 may be omitted in those cases wherein the foil has sufiicient stability to be self rotated or otherwise moved and possesses sufficient quenching capability to solidify and further cool the deposited liquid stream without degrading the foil surface.

Any suitable reservoir 44 provided with a nozzle 46 which may be suspended within drum 40 may be employed for applying the molten stream 48 to foil 42 while the reservoir is moved longitudinally within drum 40 at a controlled rate. The rate of movement of reservoir 44 relative to the rotary speed of drum 40 controls the angular path of the impinging metal stream. A slow rate of longitudinal movement of reservoir 44 relative to a fast rotary speed of drum 40 results in the formation of metal fibers on the foil at a very small helical angle close to 0 degrees. A more equal proportion between the above speeds results in a greater helical angle. Therefore, proper control of these conditions permits the production of fiber reinforced foil at a variety of fiber orientations within practical finite limits.

Upon reaching the oppoiste end of drum 40 relative to the end where the application of the molten stream started, the matrix foil may be removed for further handling as desired with the fiber ribbon adhered thereto.

It should be pointed out that using the cylindrical drum as described aids in obtaining the surface bonding effect that is desired in the end product. Centrifugal force acting on the fiber formed in this manner tends to hold the fiber against the foil. It is theorized that this may be a factor in obtaining the metallic or mechanical surface bonding effect that occurs between the fiber material and the foil material in the bimetallic systems investigated.

For example, molten boron has been applied to the surface of a titanium foil positioned on the inner surface of a rotating cylindrical drum. On striking the surface '4 of the titanium foil, the molten boron spread to form a relatively thin ribbon-like fiber tightly adhered to the foil after being solidified thereon. A photomicrograph of the boron fiber-titanium foil indicated evidence of a surface bonding effect with no observable alloying effect or the like.

The boron used in the above described example was of high purity (99.999 plus percent pure) and melted in a vacuum of 4X10" mm. Hg. The foil employed was 0.020 inch thick commercial purity titanium contained within an aluminum drum.

The drum and attached foil were rotated at approximately 5000 r.p.m. or at a foil surface velocity of approximately 76 feet per second.

The titanium foil was treated prior to depositing of the liquid boron by cleaning the foil surface with acetone. The surface finish of the foil was 25 to 30 microinches CLA as determined by a surface analyzer.

While not necessarily critical in all bimetallic fiber reinforced matrix systems, allowing between the fiber material and the foil is not desirable when the alloy exhibits unsatisfactory properties such as brittleness and the like. Therefore precautions must be taken to assure that undesirable alloying effects are inhibited.

We claim:

1. A method for producing a metal ribbon-fiber reinforced-metal matrix foil without the use of bonding pressure or bonding agents, said method comprising the steps of impinging one or more (a) liquid metal streams of relatively small cross-section onto a sheet metal matrix foil which is moving at a predetermined rate to form at least one discrete metal ribbon-fiber on the surface of said foil; and cooling the metal ribbon fiber formed on said foil to effect a solid metal fiber bonded in reinforcing relationship to said foil.

2. A method for producing a metal ribbon-fiber reinforced metal matrix foil without the use of bonding pressure or bonding agents, said method comprising the steps of impinging a liquid metal stream of relatively small cross-section onto a metal matrix foil detachably mounted on the inner surface of a rotating cylindrical drum; effecting relative movement of the drum longitudinally with respect to the initial point of contact of the liquid metal and the foil; and cooling the liquid metal ribbon fiber formed on the foil to a solid state adhered to the foil.

3. The method defined in claim 1 wherein the surface of said metal foil upon which the liquid metal is impinged was first cleaned using an organic solvent to remove foreign organic substances.

4. The method defined in claim 1 wherein said liquid metal is boron and wherein said metal foil is titanium.

References Cited UNITED STATES PATENTS 1,243,654 10/1917 Clark 29503 2,864,137 12/1958 Brennan 16487 X 3,623,203 11/1971 Henshaw et a1. 29419 UX 3,060,053 10/1962 Carreker et a1. l6486 X 3,632,034 1/1972 Kozak 29471.1 X

CHARLES W. LANHAM, Primary Examiner D. C. REILEY III, Assistant Examiner US Cl. X.R.

Patent No. gmn mg Dated May 22, 1973 Inventor(s) Lloyd Ea Haclonan and Carroll E. Mable It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 53, the term oppoi'ste should read --opposite w Column '4, line 20, the term "allowing read me alloying Column A, line 1 Signed and sealed this 8th day of January 197LL.

(SEAL) A'ttest:

EDWARD M.FLETCI-1ER,JR. RENE D. TEGTMEYER Attesting Officer I Acting Commissioner of Patents 

